I just finished reading through all the posts in this thread (even my earlier!) and I have an idea that I'd like to run by folks.
The setup I'm thinking of using has a mainline of ~40' of 1/8" Amsteel, four nacrobiners (made from 1/8" Amsteel) and a set of tree straps.
My present hammock has an ideal hung spread of 85". So, I would tie two butterfly knots, centered on the line, so that the ends of hitching loops are 85" apart. That would allow me to hitch my hammock (using nacrobiners) to the loops on the butterfly knots at the same angle that I like. Since I'm establishing my ideal length between the ends of the hitching loops, I can play with the length of those loops to adjust how high the ridge line is above me (6" loops would put the ridgeline higher than 1" loops)
Next, On each end of the main line I would install what would end up being 4-5' whoopie sling loops. These would attach to the tree slings with the other set of nacrobiners.
Here's what I'm thinking:
1. I know that 85" is where I want to be, so why not make that static on an unstretchable line that is heavy enough to take some serious pull?
2. By putting in-line whoopie slings on each end, I have some play in length and for centering the hammock between hang points.
The only points that I still have questions about are the nacrobiners. All that I've read about them suggests they should be more than strong enough for the load, but I have yet to do any practical tests.
What are your thoughts on all of this? Do you think that a nacrobiner would be weaker than the mainline itself? Is 1/8" overkill and 7/64" should be heavy enough? Are there any reasons to not make the hitching points static, if I know what spread I need to get the sag I like?